1. Field of the Invention
The present application generally relates to a circuit test interface, and more particularly, to a test interface of an input buffer.
2. Description of Related Art
FIG. 1 illustrates a circuit diagram of a conventional off-chip driver (OCD) and an input buffer. Referring to FIG. 1, the output terminal of the OCD 110 is coupled to a through-silicon via (TSV) 130. An input terminal of the input buffer 120 is coupled to the TSV 130 and an output terminal of the OCD 110.
Conventionally, when the OCD 110 and/or the input buffer 120 are tested, the TSV 130 is directly contacted by a test probe on a probe card, and electrical test signals are transmitted or received through the TSV 130.
In operation, the OCD 110 is attached to other electrical components through the TSV 130 which is traditionally the only 110 port to the circuit in FIG. 1. The TSV 130 has a relatively low maximum pin capacitance specification. Since the surface area of a TSV 130 is relatively small, conventional test probes may not be able to reliably probe. In one conventional embodiment, a conventional test pad might be attached to the TSV 130 with an on die metal trace. This embodiment would traditionally not be used in functional mode but only in a test mode, because, among other things, the test probe pad has a relatively large parasitic capacitance associated with it. Therefore, the conventional TSV 130 probing test method would tend to cause the TSV 130 to have an observed capacitance that is much greater than the relatively low maximum pin capacitance specification.